| 摘要 |
PROBLEM TO BE SOLVED: To obtain the thickness dimension of a boss part over the ceiling value at the time of integrally forming the boss part in the center part of a planar work by ironing method. SOLUTION: By moving a forming roller 4 from the inside of the work W to the outside under an indentation h1 of the roller, metal is collected and a protrusion 5 having a chevron-shaped cross section is annularly formed. (A) The forming roller 4 is once separated from the work W and situated on the outside of the protrusion 5. (B) Next, the forming roller is moved from the outside of the work W toward the inside. Consequently, by gradually making the protrusion 5 rise while furthemore growing it, the sleeve-shaped boss part 6 having a large thickness dimension S is formed.
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